This invention relates generally to coincidence detection circuits and more particularly to a multichannel coincidence detector and controller for detecting coincidence of preselected amplitude pulses occurring within a preselected time frame.
In the analysis of multichannel data collected during fracturing of oil fields resulting from high-pressure water injection, it is necessary to map fracture propagation to obtain a knowledge of the induced fissure characteristics vital in the promotion of oil well production. To determine the location and progression of fractures in an oil field while water is being injected at high pressure into one well, passive acoustic sensors are placed in surrounding wells to listen for microseisms during fracturing tests. The analog outputs from the sensors are normally recorded on a magnetic tape for later data reduction. Considerable footage of recorded magnetic tape is collected during an injection experiment which must be edited and analyzed. The signals of interest occur infrequently and at random and may best be identified by coincidences occurring within a certain time frame over one or more channels.
It has been the practice in the art to play the analog data tapes back into a multichannel oscilloscope or high-speed strip chart recorder to locate coincidences. Neither method has been very reliable because of considerable time consumed requiring an operator to constantly view the oscilloscope or strip chart to locate coincidences. Further, the strip chart recorder uses an exorbitant amount of expensive recording paper. Thus, there is a need for a multiple channel device to increase speed and certainty of detecting coincidences of events in real time or during reproduction of recorded data to more reliably detect coincidences from multiple channel data recordings which is much faster and requires considerably less operator attention.